Topo-Iberia CGPS network: a new 3D crustal velocity field in the Iberian Peninsula and Morocco based on 11 years (2008–2019)

Abstract

The Topo-Iberia network covering the Spanish part of the Iberian Peninsula and Morocco was established in 2008. Following the first publication of the horizontal velocity field based on an analysis of the first 4 years (2008–2012) in 2015, a new 3D velocity field based on 11 years (2008–2019) is presented. The double-differencing technique is applied with GAMIT software, and the precise point positioning (PPP) technique is applied with GipsyX software for GPS processing to obtain loosely constrained solutions. Then, a kalman filter is used to merge both solutions using GLOBK software and produce a velocity solution. The combined velocity solution is presented as a new horizontal velocity field and the first vertical velocity field of the Topo-Iberia CGPS network. A global view of the data quality from the Topo-Iberia stations is also presented for the first time, as well as a program specifically created to convert GipsyX gdcov files to SINEX files, gdcov2sinex.sh. The results in the IGb14 reference frame are in good agreement with previous publications, except in the Betic Cordillera, where the new velocities with respect to Eurasia are generally lower and present a higher southwestward component rather than a purely westward motion. The main discrepancy is observed at the ALJI station, where the maximum velocity is reached (3 ± 0.1 mm/yr), showing west-northwestward motion. The smallest and highest residual displacements with respect to Eurasia occur in northern Iberia and Morocco, respectively. The results support the conclusions of other studies that a clockwise block rotation occurs at present in the northern branch of the Gibraltar Arc. The velocities indicate a northwest-southeast convergence rate of 3.5 ± 0.1 mm/yr with respect to Nubia. A general low subsidence (mean value of 0.5 ± 0.1 mm/yr) is observed in the Iberian Peninsula except for some isolated stations presenting uplift.